Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-04-24
2001-05-08
Negash, Kinfe-Michael (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06229631
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of Applications No. H09-109248, filed Apr. 25, 1997 in Japan, and No. H10-019222, filed Jan. 30, 1998 in Japan, the subject matters of which are incorporated herein by reference.
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a signal transmission system and a method for supervising the same, and more particularly, to an optical transmission system and a method for supervising the same using a simulator.
BACKGROUND OF THE INVENTION
In the recent years, an optical transmission system using an optical amplifier, which directly amplifies a light signal without converting it it into an electric signal has been increasingly employed. For increasing the amount of light signals to be transmitted through a single optical amplifier, a wavelength multiplex type and a two-way transmission type of optical amplifiers have been proposed. Such an optical amplifier directly amplifies a light signal in analog fashion using an excitation light without converting it the light signal into an electric signal. When such an optical amplifier is used in a linear repeater, a supervisory light is provided in addition to a main signal to supervise the optical amplifier. The supervisory light is converted into an electric signal.
A conventional optical transmission system usually includes an optical transmitter, an optical switching device, etc. In such an optical transmission system each device is provided with a loop-back circuit to control the system. When a serious problem, such as a signal loss or out-of-frame occurs, the loop-back circuit detects and determines a location of the trouble. The location of the trouble would be in the optical transmitter, an optical receiver, an optical fiber, and the like.
In the conventional optical transmission system, when a bit-error occurs, an alarm is created and the current transmission line having the error is changed to an auxiliary line. Then, the element (package) that caused the trouble is detected and is changed.
According to the above-described conventional optical transmission system, even if trouble occurs at only one location on the current transmission line, an auxiliary line is used instead.
To decrease the opportunities of changing inferior devices, each device, such as an optical transmitter, an optical receiver and an optical repeater, needs to have enough margin for itself. If it does, it is difficult to have a wide range of system margin for the whole system.
In an optical transmission system using an optical amplifier, when a high power light is supplied into an optical transmission line, enough SN margin can be obtained. However, in response to the high power input light, an undesirable non-linear effect is generated in the optical transmission line. Such a non-linear effect influences deterioration of transmission quality. In this situation, when an output power of the optical amplifier is changed, it gets more difficult to have enough range of system margin.
If the transmission system does not have enough system margin, a plurality of alternative transmission lines has to be prepared. Even if the current transmission line has a small problem, the transmission line has to be changed to another one, because the system margin of each transmission line is small.
OBJECTS OF THE INVENTION
Accordingly, an object of the invention is to provide a transmission system, which is able to obtain a large range of system margin.
Accordingly, an object of the invention is to provide a method for supervising a transmission system so that the system has a large range of margin as a whole.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, a signal transmission system includes an interface unit that monitors the operating condition of each device. The signal transmission system also includes a simulator that simulates the transmission quality of the system in response to the operating condition of each device, and controls each device so as to optimize the transmission quality.
According to a second aspect of the invention, an optical transmission system includes interface units that detect predetermined estimation parameters from the optical transmitter, the repeater and the optical receiver. The optical transmission system includes a simulator that simulates the transmission quality of the system in response to the estimation parameters supplied from the interface units. The simulator also controls each of the optical transmitter, the repeater and the optical receiver so as to minimize a bit-error rate or to maximize a Q-factor.
According to the invention, predetermined estimation parameters are monitored from each device to estimate (calculate) a bit-error rate or Q-factor. Then, the simulator calculates the optimum control values so as to minimize the bit-error rate or to maximize the Q-factor, and controls each device in accordance with the optimum control values. As a result, the optical transmission system has the maximum system margin. Therefore, even if some devices operate out of their margin, the transmission system still operates in a range of its system margin as a whole. Consequently, it is not always required to establish an auxiliary line in addition to the main transmission line.
REFERENCES:
patent: 5173896 (1992-12-01), Dariano
patent: 5367394 (1994-11-01), Chuter et al.
patent: 5969840 (1999-10-01), Roberts
Asabayashi Issei
Maeda Hidenari
Sato Hideaki
Watanabe Takashi
Negash Kinfe-Michael
OKI Electric Industry Co., Ltd.
Wenderoth Lind & Ponack LLP
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